Simulator apparatus with at least two degrees of freedom of movement for an instrument

ABSTRACT

A simulator apparatus with at least two degrees of freedom of movement for an instrument that has an elongated shaft, having a holding device for the instrument, the holding device being designed such that the instrument has at least a first degree of freedom of a swiveling movement about a first swivel axis and at least a second degree of freedom of swiveling movement about a second swivel axis, running perpendicular to the first swivel axis. The holding device has a cardanic suspension that has a spherical element which is suspended such that it can rotate about the first swivel axis and about the second swivel axis, and in which the shaft is partly held.

CROSS-REFERENCE TO PENDING APPLICATIONS

[0001] The present application is a continuation of pendingInternational patent application PCT/EP01/12649 filed on Oct. 31, 2001which designates the U.S., and which claims priority of German patentapplication DE 100 55 292.7 filed on Nov. 03, 2000.

BACKGROUND OF THE INVENTION

[0002] The invention relates to a simulator apparatus with at least twodegrees of freedom of movement for an instrument that has an elongatedshaft comprising a holding device for the instrument, the holding devicebeing designed such that the instrument has at least a first degree offreedom of a swivelling movement about a first swivel axis and at leasta second degree of freedom of swivelling movement about a second swivelaxis, running perpendicular to the first swivel axis.

[0003] Such a simulator apparatus is known for example from U.S. Pat.No. 6,024,576.

[0004] In general, such a simulator apparatus is used as interfacebetween an operator and an instrument in simulators. A specific use, towhich the following description relates without limiting the presentinvention thereto, is the integration of a simulator apparatus mentionedat the beginning in a simulator for simulating a minimally invasivesurgical intervention in a human or animal body.

[0005] The term “instrument” is to be understood generally in the senseof the present invention, and in the case of a medical simulation, itcan be an endoscope, a tool such as scissors, forceps, a dissector,clamp applicator etc.

[0006] In recent years, minimally invasive surgery has gained clearly inimportance by comparison with open surgery. In minimally invasivesurgery, a viewing system, for example an endoscope, and one or moreinstruments such as forceps, scissors, HF instruments, clampapplicators, etc. are introduced into the body by minimal incisions. Theminimally invasive surgical operation is carried out with videoassistance with the aid of the abovementioned instruments in combinationwith peripheral devices.

[0007] At present, minimally invasive surgery is used, for example, forremoving a gall bladder, the appendix and for handling herniotomies.Further fields of use are being opened up.

[0008] However, “minimally invasive” surgery covers as a term not onlysurgical interventions, but also interventions such as, for example, theintroduction of substances into the body, or biopsies where use is madeof the minimally invasive technique.

[0009] By contrast with open surgery, the advantage of the minimallyinvasive technique resides in the mode of procedure, which spares thepatient and entails less surgical trauma, shorter times of stay inhospitals and a shorter incapability for work.

[0010] By contrast with open surgery, however, the handling of theinstruments during a surgical intervention is substantially morecomplicated, firstly because the freedom of movement of the instrumentinserted through the incision is restricted because of the only smallincision, and secondly because the surgeon does not himself have a cleardimensional view of the working tip of the instrument located in thebody, nor of the operating site, but instead only a two-dimensionalvisual monitoring is possible via the video monitor. It goes withoutsaying that the coordination of the guidance and operation of theinstrument or instruments are thereby rendered more difficult.

[0011] There is thus a greater need for training in the new techniquesof minimally invasive surgery. Various alternatives currently exist fortraining in surgical procedures of minimally invasive surgery.

[0012] One alternative consists in carrying out training operations invivo on animals, specifically on pigs. However, such training is costintensive, time consuming to prepare and, moreover, ethically dubious.

[0013] In the case of a further alternative, physicians are trained onin vitro organs in a training box into which the instruments can beappropriately introduced. The organs arranged in the training box arecertainly biological organs, but training in the case of thisalternative is likewise time consuming to prepare and cannot be regardedas realistic.

[0014] Finally, training in minimal invasive surgery is currently beingcarried out on model organs or training objects in a training box.However, such model organs are not sufficiently realistic for trainingfor an entire operation. Moreover, the preparation of the model organsand training objects requires a not inconsiderable preparatory outlay,since the models are for the most part destroyed during the operationand initially require to be prepared again for further trainingsessions.

[0015] Because of the disadvantages of the training systems used todate, there was already a need very early for so called virtualsimulators that can be used to overcome the disadvantages of theprevious training systems.

[0016] The actual operating site is generated exclusively via a computerin the case of virtual simulation. Realistic simulation requires a modeldatabase that fixes the geometric shapes and physical properties of thetissues, organs and vessels, as well as the geometry and kinematics ofthe instrument or instruments. In the journal “Biomedical Journal”,Volume No. 51, April 1998, U. Kühnapfel describes a“Virtual-Reality-Trainingssystem für die Laparoskopie” [“Virtual realitylaparoscopy training system”] that has an input box which exhibits fromthe outside the customary instrument grips and a virtual endoscope. Inthe housing, the minimally invasive instruments are guided in amechanical guide system that further permits the detection of thedeflection of the instruments and actuators. In addition, various footswitches are present that can be used to activate surgical and generalfunctions. Via angle encoders, for example, a PC-based sensor dataacquisition process measures the positions of the joints of theoperating instruments and transmits these continuously to a graphicsworkstation. A “virtual” image of the endoscope view is calculated therefrom in real time. The consistency of the tissue to be treated is fedback to the operator realistically as force feedback by inherentlycalculated “virtual” reactive forces between organs and instruments.

[0017] Consequently, in the case of virtual simulation of minimallyinvasive interventions, no use is made of physically presentorgans—instead the spatial and physiological structures of such organsare present as data in a computer. The simulator apparatus mentioned atthe beginning in this case forms the interface between the operator andthe instrument to be handled and the simulation computer system. Theoperator to be trained handles the instrument accommodated in themechatronic simulator apparatus, the data stored in the computer, forthe spatial and physiological structure of the virtual organ beingtransmitted as force feedback by the simulator apparatus to theinstrument while the latter is being handled, as a result of which theoperator is afforded a realistic feel.

[0018] The previous developments in this field have concentratedprimarily on the creation of the simulation software, while so faravailable holding systems capable of localization have been used asmechatronic simulator apparatus. In the interests of realisticsimulation, the simulator apparatus should take account of all degreesof freedom that are present for a minimally invasive surgicalinstrument, specifically a tilting of the instrument about the surfaceof the body, a movement in the direction of the shaft and a rotarymovement about the longitudinal axis of the shaft. However, a problem inthis is the mechanical implementation of these many degrees of freedomin the holding device of the simulator apparatus for the instrument.

[0019] For example, the simulator apparatus known from U.S. Pat. No.6,024,576 cited above comprises a complicated mechanical lever systemwhose disadvantage resides particularly in the fact that the simulatorapparatus is very large overall. It is therefore impossible using such asimulator apparatus for two or more apparatuses to bring a plurality ofinstruments so close together that the instrument tips can touch.Because of the many levers used in this known simulator apparatus,undesirable moments of inertia and torques occur when this simulatorapparatus is being used and must be compensated in a complicated way inorder to permit a realistic force feedback.

[0020] WO 96/30885 discloses a virtual surgical system for simulatingsurgical interventions on the basis of image data. It is possiblethereby to simulate a surgical procedure by using the image data of apatient, it being possible to simulate the instruments used by a surgeonin carrying out an actual procedure. This known apparatus makes use asinput apparatus of a mouse, a three-dimensional mouse, a joystick or aseven-dimensional joystick. The joystick provided in the known apparatusis designed in the form of a lever at whose lower end a ball is arrangedthat can be rotated in various directions of solid angle in a ball cup.However, a mouse or a joystick does not correspond to the application ofan actual surgical instrument.

[0021] Further, EP-0 970 662 A1 discloses a simulator apparatus forsimulating the insertion of a catheter into blood vessels. The simulatedcatheter has only degrees of freedom of rotation about the longitudinalaxis of the catheter, and of translatory movement in the direction ofthe longitudinal axis of the catheter. Provided for the purpose ofachieving a force feedback is a gear arrangement that has, inter alia, adifferential gear which, however, is arranged with reference to thelongitudinal central axis of the catheter in a fashion laterally apartand aside from the latter, and which is connected to the catheter viavarious stands and holding devices.

[0022] It is therefore the object of the invention to specify asimulator apparatus of the type mentioned at the beginning that has acompact design and mechanics of low torque.

SUMMARY OF THE INVENTION

[0023] According to the invention, a simulator apparatus with at leasttwo degrees of freedom of movement for an instrument that has anelongated shaft, is provided, comprising:

[0024] a holding device for holding said instrument, said holding devicebeing designed such that said instrument has at least a first degree offreedom of swivelling movement about a first swivel axis and at least asecond degree of freedom of swivelling movement about a second swivelaxis, said second swivel axis running perpendicular to said first swivelaxis,

[0025] said holding device having a cardanic suspension, said cardanicsuspension having a spherical element in which said shaft of saidinstrument is partly received, said spherical element being suspendedsuch that it can rotate about said first swivel axis and about saidsecond swivel axis.

[0026] The simulator apparatus according to the invention therefore hasa cardanic suspension for the instrument that has the advantage of theparticularly low-torque guidance of the instrument in the holdingdevice. The cardanic suspension permits the superimposition of theswivelling movements of the instrument both about the first swivel axisand about the second swivel axis. While in the case of a realintervention an operating instrument can usually be swivelled about theplane of the body surface about two axes that are perpendicular to oneanother and intersect in the incision, the simulator apparatus accordingto the invention permits a realistic simulation of such manipulations ofan instrument.

[0027] In a preferred refinement, the cardanic suspension is formed by abow-shaped element that can be swivelled about the first swivel axis,and an annular element, connected to the spherical element, that canswivel about the second swivel axis, the instrument being guided on thebow-shaped element.

[0028] This refinement implements a cardanic suspension that is ofparticularly simple design and has the further advantage that in thecase when, as provided in a further preferred refinement, the simulatorapparatus is provided with a first feedback for the first and seconddegrees of freedom, the corresponding actuators for the force feedbackcan be provided in a fixed fashion on the apparatus and therefore neednot be moved as well, as a result of which particularly low-torquemechanics of the simulator apparatus can be achieved.

[0029] In a further preferred refinement, there are fastened on theannular element two mutually opposite seats, arranged offset byapproximately 90° with reference to the second swivel axis, for thespherical element, the spherical element in the seats being held suchthat it can rotate relative to the seats about an axis of rotationpassing through both seats, and such that it is immobile with referenceto the seats perpendicular to this axis of rotation.

[0030] By means of this measure the advantage is achieved that theinstrument itself need be guided only at the bow-shaped element withreference to a swivelling movement about the first swivel axis, whilethe guiding of the instrument with reference to the swivelling movementabout the second swivel axis is accomplished via the spherical element,the seats and, via these, the annular element.

[0031] As already mentioned, the first degree of freedom and the seconddegree of freedom are provided with a force feedback, there beingprovided in a further preferred refinement for the force feedback forthe first and second degrees of freedom in each case at least oneactuator, that acts on the bow-shaped element and the annular element.

[0032] Actuators also moved can advantageously be avoided by thepreviously described refinement.

[0033] In a further preferred refinement, the holding device is designedsuch that the instrument has a third degree of freedom of rotatingmovement about the longitudinal axis of the shaft, and a fourth degreeof freedom of translatory movement in the direction of the shaft.

[0034] Due to the abovementioned refinement, the simulator apparatusaccording to the invention advantageously also permits, in a realisticfashion, movements of an instrument in the direction of the longitudinalaxis and rotary movements about the longitudinal axis of the shaft. Thesimulator apparatus according to the invention thus permits at leastfour degrees of freedom of movement for the instrument.

[0035] It is preferred in this case if the holding device has for thethird and fourth degrees of freedom a gear arrangement that has a firstbevel gear, which is connected to the shaft and co-rotates with thelatter about the longitudinal axis thereof, and has a second and a thirdbevel gear which are arranged on either side of the first bevel gear andare in rolling engagement therewith.

[0036] The simulator apparatus according to the invention therefore has,for the third and fourth degree of freedom, a gear arrangement thatresembles a differential gear and has the advantage that it can bearranged around the shaft of the instrument and is of particularly smalloverall size, and in particular large radii of movement of the movingparts such as in the case of the known lever arrangements are avoided.Guiding of the instrument in the holding device with particularly lowtorque is thereby also achieved. As stated in a further preferredrefinement, the gear arrangement can be used both to implement thedegree of freedom of the rotary movement about the longitudinal axis ofthe shaft and the degree of freedom of the translatory movement in thedirection of the shaft with a force feedback, and also a superimpositionof the two movements is rendered possible with low torque by the geararrangement provided according to the invention. Moreover, the geararrangement with three bevel gears has the advantage that the actuators,for example electric motors, possibly present for a force feedback, canbe arranged immovably in the simulator apparatus, the result being toavoid further moments of inertia and torque, and to avoid a greaterspace requirement for the movement of such motors.

[0037] In a further preferred refinement, the first bevel gear is inrolling engagement with the shaft via one or more pinions with the aidof a tooth system extending along the shaft.

[0038] A translatory movement of the shaft along its longitudinal axisonto the first bevel gear is effected with particularly low torque bymeans of this measure. In the case of such a longitudinal movement ofthe shaft, the first bevel gear is set rotating about its longitudinalaxis, and this thereby sets the second and the third bevel gears inrotary movements of mutually opposite direction. Force feedback to thedegree of freedom of the rotary movement about the shaft can thereforebe implemented with particular ease by providing the second and thirdbevel gears, which are retarded by one or more actuators, as in afurther preferred refinement. In order to achieve force feedback to thedegree of freedom of the translatory movement, the second and the thirdbevel gears are then driven in opposite directions with the same torqueand at the same speed.

[0039] However, the same actuators can also be used to achieve forcefeedback to the degree of freedom of the rotary movement of the shaftabout its longitudinal axis. Specifically, as already mentioned when theinstrument is being rotated about its longitudinal axis the first bevelgear is also corotated about the longitudinal axis of the shaft and, inthe process, this sets the second and the third bevel gears in rotarymovements in the same direction. In order to achieve force feedback tothe degree of freedom of the rotary movement of the shaft about itslongitudinal axis, the actuators must therefore retard the second andthe third bevel gears in the same direction and with the same torque.

[0040] In a further preferred refinement, the second and the third bevelgears are arranged concentrically with the shaft.

[0041] This arrangement of the second and third bevel gears results in aparticularly space-saving design, of small overall size, of the geararrangement and of the overall arrangement of shaft and geararrangement.

[0042] In a further preferred refinement, the gear arrangement isarranged in the spherical element.

[0043] A particularly space-saving design of the overall simulatorapparatus is achieved by this measure despite the at least four possibledegrees of freedom of the movement of the instrument. Because of itsarrangement in the spherical element, the gear arrangement executes theswivelling movements about the first and second swivel axes togetherwith the instrument. The gear arrangement is therefore suspended in acardanic fashion in a particularly space-saving Way.

[0044] In a further preferred refinement, in each case one-positiondetection sensor is provided for determining the position of theinstrument for at least one degree of freedom, preferably for alldegrees of freedom.

[0045] The instantaneous values of all degrees of freedom of theinstrument which are rendered possible by the simulator apparatusaccording to the invention can be detected in real time with the aid ofsuch position detection sensors, and can be used, in turn, to generatesignals for the force feedback in real time in a computer by appropriatesignal processing.

[0046] In a further preferred refinement, the instrument has a moveableoperating device and the moveable operating device is equipped withforce feedback.

[0047] Particularly when the instrument is not an endoscope, but asurgical instrument such as forceps or scissors, this measure has theadvantage that the simulator apparatus according to the invention canalso simulate the force resistances occurring during the realpreparation, for example cutting or grasping, of tissue. In the simplestcase, it is possible to attach to the moveable operating device a Bowdencable that is connected to an actuator which, in turn, receives controlsignals from the simulation computer system. With the refinementmentioned previously, the simulator apparatus according to the inventioneven has five degrees of freedom for the simulation.

[0048] In a preferred use of the simulator apparatus, the latter is usedto simulate a minimally invasive operation on the human or animal body.

[0049] Further features and advantages emerge from the followingdescription and the attached drawing.

[0050] It goes without saying that the features mentioned above andthose still to be explained below can be used not only in therespectively specified combination, but also in other combinations or ontheir own, without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] An exemplary embodiment of the invention is illustrated in thedrawings and will be described in more detail hereafter with referencethereto. In the drawings:

[0052]FIG. 1 shows an overall perspective illustration of a mechatronicsimulation apparatus for simulating at least two degrees of freedom ofmovement of an instrument with force feedback;

[0053]FIG. 2 shows the simulator arrangement in FIG. 1 in an operatingposition changed from FIG. 1;

[0054]FIG. 3 shows the simulator apparatus in FIGS. 1 and 2 in a furtheroperating position changed from FIGS. 1 and 2;

[0055]FIG. 4 shows a side view of the simulator apparatus in FIGS. 1 to3 with partial omissions and partly in section;

[0056]FIG. 5 shows a further side view of the simulator apparatus inFIGS. 1 to 4, the side view being rotated by approximately 90° bycomparison with FIG. 4;

[0057]FIG. 6 shows a gear arrangement, present in the simulatorapparatus in FIGS. 1 to 5, in perspective illustration to an enlargedscale;

[0058]FIG. 7 shows a detail of the simulator apparatus in FIGS. 1 to 5in a longitudinal section to an enlarged scale; and

[0059]FIG. 8 shows a section along the line VIII-VIII in FIG. 7.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0060] A simulator apparatus, provided With the general reference 10,for simulating at least two degrees of freedom or movement of aninstrument 12 is illustrated in FIGS. 1 to 5.

[0061] The simulator apparatus 10 is used, in particular, to simulateminimally invasive surgical operations on the human or animal body forthe purpose of training physicians.

[0062] The instrument 12 is a pair of preparation forceps for cuttingtissue in the exemplary embodiment shown. Instead of such preparationforceps, it is also possible, however, for an endoscope to be insertedas instrument 12 into the simulator apparatus 10, or it is possible toinsert other tools such as clamp applicators, suction and irrigationinstruments and the like into the simulator apparatus 10. The instrument12 can be removed from the simulator apparatus for the purpose ofchanging instruments.

[0063] The instrument 12 has, in general, an elongated shaft 14 that ispassed through the simulator apparatus 10 or is accommodated therein, atool 16 at the distal end of the shaft which, in the present exemplaryembodiment, has two jaw parts, for example provided with cutting edges,and a grip 18 at the proximal end of the shaft 14. An operating device18 has a moveable grip part 20 and an immovable grip part 22.

[0064] The simulator apparatus 10 has a holding device 24, which will beexplained in more detail below.

[0065] The holding device 24 has a cardanic suspension 25. The cardanicsuspension 25 permits the simulation of a degree of freedom ofswivelling movement of the instrument 12 about a first swivel axis 26,as well as of a further degree of freedom of swivelling movement of theinstrument 12 about a second swivel axis 28, running perpendicular tothe first swivel axis 26. With the aid of these two degrees of freedom,it is possible to simulate any desired tilted positions of theinstrument 12 with reference to a surface 30, which simulates the bodysurface of a patient in the case of a use of the simulator apparatus 10to simulate minimally invasive operations on the human or animal body.The point of intersection between the swivel axes 26 and 28, which liesat a point on the longitudinal axis of the shaft 14, constitutes theinvariant point of the swivelling movements of the instrument 12. Sincein the case of real minimally invasive surgery the instrument is guidedthrough an incision in the body surface, and the invariant point liesapproximately in the incision, the arrangement of the swivel axes 26 and28 is made in the case of the simulator apparatus 10 such that the pointof intersection lies approximately at the level of the surface 30 orslightly there below.

[0066] In order to implement the swivel axis 26 of the cardanicsuspension 25, the cardanic suspension 25 has a bow-shaped element 32that is designed approximately in a shape of a semicircle. Thebow-shaped element 32 is mounted swivelably about the swivel axis 26 ona mounting frame 34 (FIGS. 4 and 5) which is itself immovable.

[0067] In order to implement the swivel axis 28, the cardanic suspension25 has an annular element 36 that is arranged inside the bow-shapedelement 32. The annular element 36 is suspended about the second swivelaxis 28 by means of mounting angles 38 and 40.

[0068] Furthermore, there are fastened to the annular element 36 twomutually opposite seats 42 and 44 that are arranged offset byapproximately 90° with reference to the second swivel axis 28. The seats42 and 44 are designed as spherical shell segments and accommodate aspherical element 46.

[0069] The shaft 14 of the instrument 12 is accommodated in thespherical element 46 and goes through the latter, as will be explainedin more detail later.

[0070] The spherical element 46 is mounted in the seats 42 and 44 bymeans of two pins 48 and 50 (indicated by broken lines) that engage incorresponding bores in the spherical element 46. The spherical element46 can thus be rotated relative to the seats 42 and 44 about an axis ofrotation 52 defined by the pins 48 and 50, but is immovable withreference to the seats 42 and 44 at right angles to this axis ofrotation 52. Overall, the spherical element 46 can be moved relative tothe bow-shaped element 32, and also relative to the annular element 36.

[0071] The shaft of the instrument 14 is guided only in the bow-shapedelement 32, but not in the annular element 36. For this purpose, theshaft 14 is guided in the bow-shaped element 32 via a sleeve 52 thatprojects through an elongated hole 54 formed in the bow-shaped element32. The shaft 14 can move together with the sleeve 52 in thelongitudinal direction of the elongated hole 54 when the instrument 12is swivelled about the second swivel axis 28.

[0072] Both the degree of freedom of the swivelling movement about thefirst swivel axis 26 and the degree of freedom of the swivellingmovement about the second swivel axis 28 are provided in each case withforce feedback.

[0073] An actuator, for example a DC motor for force feedback to thebow-shaped element 32, is arranged for the bow-shaped element 32, whichelements 32 can be swivelled about the first swivel axis 26. A positiondetection sensor 58, for example in the form of a potentiometer or anincremental rotary encoder, is arranged opposite the actuator 52 for thepurpose of detecting position, that is to say for determining the angleof the angular position of the bow-shaped element 32.

[0074] Correspondingly, as force feedback for the degree of freedom ofthe swivelling movement about the second swivel axis 28 a furtheractuator 60 is connected to the annular element 36 via the mountingangle 40, and a position detection sensor 62 is connected via themounting angle 38.

[0075] The mode of operation of the cardanic suspension 25 without andwith force feedback is therefore as follows. An operator, for example aphysician to be trained, takes hold of the operating device 18 of theinstrument 12 in one hand. By moving the operating device 18, theinstrument 12 can now be tilted in arbitrary solid angle directionsabout the plane 30 about the invariant point formed by the point ofintersection of the first swivel axis 26 with the second swivel axis 28.This is illustrated by way of example in FIGS. 1 to 3 with the aid ofvarious tilted positions.

[0076] From the tilted position in FIG. 1, the instrument 12 was tiltedabout the second swivel axis 28, while the swivel position remainsunchanged with reference to the first swivel axis 26. In the event ofthis movement, the annular element 36 has been tilted correspondinglyabout the second swivel axis 28, while the spherical element 46 haschanged its position relative to the bow-shaped element 32, but notrelative to the annular element 36. In the drawing, the sleeve 52 withthe shaft 14 has been moved correspondingly to the right in theelongated hole 54 of the bow-shaped element 32.

[0077] Starting from FIG. 2, the tilted position illustrated in FIG. 3is reached by having swivelled the instrument 12 in a direction into theplane of the drawing about the first swivel axis 26. In this case, theannular element 36 has not been moved, but the spherical element 48 hasmoved relative to the annular element 36.

[0078] In order in the case of the above described movements of theinstrument 12 to simulate a force resistance that is to be overcome, forexample, by the elasticity, stiffness of a simulated tissue whenhandling the instrument 12, the above mentioned movements can becounteracted by a software-aided computer-controlled drive of theactuators 56 and 60, such that the operator feels a “real” forceresistance as if he is carrying out the same actions on a patient.

[0079] The position detection sensors 58 and 62 continuously detect inreal time the current angular positions of the instrument 12 about thefirst swivel axis 26 and second swivel axis 28, and the actuators 56 and60 are driven for force feedback in real time on the basis of these dataand the tissue data stored in the computer.

[0080] It goes without saying that the instrument 12 can be swivellednot only sequentially about the first swivel axis 26 and the secondswivel axis 28, but also simultaneously in any desired solid angledirections about both swivel axes 26 and 28.

[0081] It follows from the above that the actuators 56 and 60, as wellas the position detection sensors 58 and 62 were not also moved duringthe movements of the instrument 12 and the movements, associatedtherewith, of the annular element 36, the bow-shaped element 32 and thespherical element 46, and so the holding device 24 is of very low torqueand the cardanic suspension 25 constitutes a very compact design forimplementing the previously named degrees of freedom.

[0082] In accordance with a further aspect, the simulator apparatus 10has a gear arrangement 70, which will be described in more detail belowwith reference to FIGS. 6 to 8.

[0083] The gear arrangement 70 is a component of the holding device 24for the instrument 12, it being possible to use the gear arrangement 70to simulate further degrees of freedom of movement for the instrument 12with force feedback. These further degrees of freedom are a degree offreedom of rotary movement of the instrument 12 about the longitudinalaxis of the shaft 14, and a further degree of freedom of translatorymovement of the instrument 12 in a direction of the shaft 14.

[0084] As emerges from FIGS. 7 and 8, the gear arrangement 70 providedfor simulating the two above named degrees of freedom with forcefeedback is arranged as a whole in the spherical element 46 of thecardanic suspension 25. The gear arrangement 70 is illustrated inperspective in FIG. 6 to a large scale without the spherical element 46.

[0085] Firstly, the gear arrangement 70 has a first bevel gear 72. Thefirst bevel gear 72 can be rotated about an axis of rotation 74 runningtransverse to the shaft 14. The first bevel gear 72 has a tooth system(not illustrated in FIG. 6) on a frustoconical circumferential surface76. The frustoconical surface 76 can also be designed as a frictionsurface instead of a tooth system.

[0086] The gear arrangement 70 further has a second bevel gear 78 and athird bevel gear 80, the second bevel gear 78 and the third bevel gear80 being arranged on either side of the first bevel gear 72. The secondbevel gear 78 and the third bevel gear 80 are arranged around the shaft14 of the instrument 12 in a fashion coaxial therewith. The bevel gears78 and 80 can therefore be rotated about the longitudinal axis of theshaft 14. The axes of rotation of the bevel gears 78 and 80 runperpendicular to the axis of rotation of the bevel gear 72.

[0087] The second bevel gear 78 has a frustoconical surface 82, and thethird bevel gear 84 has a frustoconical surface 84, the frustoconicalsurfaces 82 and 84 being in rolling engagement with the frustoconicalsurface 76 of the first bevel gear 72. The frustoconical surfaces 82 and84 correspondingly have tooth systems, or are constructed as frictionsurfaces.

[0088] While the second bevel gear 78 and the third bevel gear 80 arenot connected to the shaft 14, the first bevel gear 72 is connected tothe shaft 14 via a pinion arrangement that has a first pinion 86 and asecond pinion 88. The first pinion 86 is connected securely in terms ofrotation to the second pinion 88 via a shank 90. An axis of rotation ofthe arrangement composed of the first pinion 86, the shank 90 and thesecond pinion 88 runs parallel to the axis of rotation 74 of the firstbevel gear 72.

[0089] The first bevel gear 72 has a spur gear 92 that engages with thefirst pinion 86 in a meshing fashion.

[0090] By contrast, the second pinion 88 engages with a tooth system 94extending along the shaft 14.

[0091] The spur gear 92 can be constructed as one piece with the firstbevel gear 72, or be connected securely in terms of rotation to thelatter as a separate part.

[0092] In accordance with FIGS. 7 and 8, the gear arrangement 70 isarranged inside the spherical element 46 in a cutout 96.

[0093] The shaft 14 of the instrument 12 is guided by cylindricalsleeves 98 and 100 through the gear arrangement 70. Because of the toothsystem 94 provided on the shaft 14, the shaft 14 has a key-like profilein cross section, the gear arrangement having a keyhole-like passage 102(FIG. 8) which is complementary correspondingly thereto. The first bevelgear 72 is connected in this way to the shaft 14 securely in terms ofrotation via the pinions 86 and 88, that is to say given a rotation ofthe shaft 14 about its longitudinal axis the first bevel gear 72 in thespherical element 48 is rotated about the longitudinal axis of the shaft14 in accordance with a double arrow 104, depending on the direction ofrotation of the shaft.

[0094] The second bevel gear 78 is connected securely in terms ofrotation to an annular flange 106. The third bevel gear 80 is connectedsecurely in terms of rotation to a cylindrically constructed box 108that, in turn, is connected securely in terms of rotation to a furtherannular flange 110. The annular flange 106, which is connected securelyin terms of rotation to the second bevel gear 78, has on its outercircumference a tooth system that meshes with a pinion 112 that isconnected to the output shank of an actuator 114, for example a DCmotor.

[0095] The annular flange 110, which is connected securely in terms ofrotation to the third bevel gear 80 via the box 108, likewise has on itsouter circumference a tooth system that meshes with a pinion 114 that isconnected on the output side to an actuator 118.

[0096] The actuators 114 and 118 serve as force feedback for the degreeof freedom of the translatory movement in direction of the shaft, and asforce feedback for the degree of freedom of the rotary movement of theinstrument 12 about the shaft 14, as will be described in yet moredetail hereafter.

[0097] The mode of operation of the gear arrangement 70 is as follows,the mode of operation firstly being described without force feedback.

[0098] If the instrument 12 is rotated about the longitudinal axis ofthe shaft 14, because of the keyhole-like connection to the keyhole-likepassage 102 the shaft 14 corotates the pinions 88 and 86, and thus thefirst bevel gear 72 in the direction of rotation of the shaft 14. Thefirst bevel gear 72 is mounted in a floating fashion inside the box 108.In the event of this rotation of the first bevel gear 72 about thelongitudinal axis of the shaft 14, the first bevel gear 72 does notrotate about its axis of rotation 74. By contrast, the bevel gear 72rotating about the longitudinal axis of the shaft 14 sets the secondbevel gear 78 and the third bevel gear 80 rotating in mutually identicaldirections.

[0099] If the instrument 12 is displaced along the direction of theshaft 14 in the holding device 24, the tooth system 94 sets the pinion88 and thus the pinion 86 in a rotation that causes a correspondingrotation of the bevel gear 72 about the axis of rotation 74 without, aspreviously described, the bevel gear 72 rotating about the longitudinalaxis of the shaft 14. Because of the rotation of the first bevel gear 72about the axis of rotation 74, the second bevel gear 78 and the thirdbevel gear 80 are now set rotating in mutually opposite directions.

[0100] In order now to bring about a force feedback to the degree offreedom of the rotation of the instrument 12 about the longitudinal axisof the shaft 14, the actuators 114 and 118 must retard the second bevelgear 78 and the third bevel gear 80 in the same direction of rotationrelative to one another with the same torque.

[0101] In order to bring about a force feedback to the degree of freedomof the translatory movement of the instrument 12 in the direction of theshaft 14, because of the oppositely directed rotary movement of thesecond bevel gear 78 relative to the third bevel gear 80 the actuators118 and 114 must correspondingly retard the bevel gears 78 and 80 inopposite directions, as far as possible with the same torques, in orderthereby to oppose this degree of freedom with a force feedback.

[0102] The gear arrangement 70 has rendered it possible not to requirethe actuators 114 and 118 also to be moved. This results in animplementation also of these two degrees of freedom of the instrument 12that is of particularly low torque, and in a particularly compactdesign, since it is necessary, as far as moving parts are concerned,only for the bevel gears 72, 78 and 80 and smaller pinions to be moved.

[0103] It goes without saying that movements of the instrument 12 in thedirection of the shaft 14 and movements of the instrument 12 about thelongitudinal axis of the shaft 14 can be performed in a fashionsuperimposed on one another simultaneously.

[0104] Furthermore, position detection sensors (not illustratedindividually), for example in the form of angle encoders, are providedfor the degrees of freedom of the rotary movement about the longitudinalaxis of the shaft 14 and the translatory movement in the direction ofthe shaft 14 in order to be able to carry out computer-aided simulationwith the aid of appropriate software.

[0105] It follows from the above description that the simulatorapparatus 10 renders possible a simulation of four degrees of freedom ofmovement of the instrument 12, all the degrees of freedom being providedwith force feedback.

[0106] A fifth degree of freedom of movement consists in the case of theinstrument 12 in the movement of the moveable grip part 20. Forcefeedback can also be provided for this degree of freedom of movement,for example by connecting at the moveable grip part a Bowden cable (notillustrated) that is connected to an actuator (not illustrated) in theform of a DC motor. Appropriate position detection sensors detect thecurrent position of the moveable grip part for the purpose of real timecalculation of the force feedback.

[0107] The compact design of the simulator apparatus 10 renders itpossible to use three such apparatuses in close proximity, one simulatorapparatus, for example an endoscope, and two further apparatusesrespectively accommodating a tool. The compact design of the simulatorapparatus 10 even renders it possible in this case for the instrumenttips to be able to touch one another, as is the case with real surgicaloperations.

[0108] Via a measured data acquisition and control card the simulatorapparatus 10 is connected (in a way not illustrated) in a unit to acentral processor. Stored in a program in the measured data acquisitionand control card are the kinematics for determining the position of theinstrument tip, of the tool 16 in the case of the instrument 12, and theinverse kinemetics for the distribution of the force and torquecomponents at the instrument tip, as well as a software for the control.

[0109] The previously described actuators are to be understood only byway of example, it also being possible to implement such motors by meansof hollow-shank motors. Moreover, instead of one axial hollow-shankmotor acting coaxially, it is possible for a plurality of motors to actcoaxially on the bevel gears 78 and 80.

What is claimed is:
 1. A simulator apparatus with at least two degreesof freedom of movement for an instrument that has an elongated shaft,said simulator apparatus comprising: a holding device for holding saidinstrument, said holding device being designed such that said instrumenthas at least a first degree of freedom of swivelling movement about afirst swivel axis and at least a second degree of freedom of swillingmovement about a second swivel axis, said second swivel axis runningperpendicular to said first swivel axis, said holding device having acardanic suspension, said cardanic suspension having a spherical elementin which said shaft of said instrument is partly received, saidspherical element being suspended such that it can rotate about saidfirst swivel axis and about said second swivel axis, said cardanicsuspension further being formed by a bow-shaped element that can beswivelled about said first swivel axis, and an annular element,connected to said spherical element that can swivel about said secondswivel axis, wherein said instrument is guided on said bow-shapedelement, two mutually opposite seats for said spherical element beingfastened on said annular element and arranged offset by approximately90° with reference to said second swivel axis, said spherical elementbeing held in said seats such that it can rotate relative to said seatsabout an axis of rotation passing through both seats while it isimmobile with reference to said seats perpendicular to said axis ofrotation.
 2. The simulator apparatus of claim 1, wherein said firstdegree of freedom and said second degree of freedom are provided withforce feedback.
 3. The simulator apparatus of claim 2, wherein there isprovided for said force feedback for said first and second degrees offreedom in each case at least one actuator that acts on said bow-shapedelement and said annular element.
 4. The simulator apparatus of claims1, wherein said holding device further is designed such that saidinstrument has a third degree of freedom of rotating movement about saidlongitudinal axis of said shaft and a forth degree of freedom oftranslatory movement in the direction of said shaft.
 5. The simulatorapparatus of claim 4, wherein said holding device has for said first andsaid forth degrees of freedom a gear arrangement that has a first bevelgear, which is connected to said shaft of said instrument and co-rotateswith the latter about the longitudinal axis thereof, and has a secondand a third bevel gear which are arranged on either side of said firstbevel gear and are in rolling engagement therewith.
 6. The simulatorapparatus of claim 5, wherein said gear arrangement is arranged in saidspherical element.
 7. The simulator apparatus of claim 1, wherein eachcase one-position detection sensor is provided for determining theposition of said instrument for at least one degree of freedom.
 8. Thesimulator apparatus of claim 1, wherein said instrument has a movableoperating device, said movable operating device being equipped withforce feedback.
 9. A simulator apparatus with at least two degrees offreedom of movement for an instrument that has an elongated shaft, saidsimulator apparatus comprising: a holding device for holding saidinstrument, said holding device being designed such that said instrumenthas at least a first degree of freedom of swivelling movement about afirst swivel axis and at least a second degree of freedom of swivellingmovement about a second swivel axis, said second swivel axis runningperpendicular to said first swivel axis, said holding device having acardanic suspension, said cardanic suspension having a spherical elementin which said shaft of said instrument is partly received, saidspherical element being suspended such that it can rotate about saidfirst swivel axis and about said second swivel axis.
 10. The simulatorapparatus of claim 9, wherein said cardanic suspension is formed by abow-shaped element that can be swivelled about said first swivel axis,and an annular element connected to said spherical element, that canswivel about said second swivel axis, said instrument being guided onsaid bow-shaped element.
 11. The simulator apparatus of claim 10,wherein there are fastened on said annular element two mutually oppositeseats, arranged offset by approximately 90° with reference to saidsecond swivel axis, for said spherical element, said spherical elementin said seats being held such that it can rotate relative to said seatsabout an axis of rotation passing through both seats, and such that itis immobile with reference to said seats perpendicular to said axis ofrotation.
 12. The simulator apparatus of claim 9, wherein said firstdegree of freedom and said second degree of freedom are provided withforce feedback.
 13. The simulator apparatus of claim 12, wherein thereis provided for said force feedback for said first and second degrees offreedom in each case at least one actuator that acts on said bow-shapedelement and said annular element.
 14. The simulator apparatus of claim9, wherein said holding device further is designed such that saidinstrument has a third degree of freedom of rotating movement about saidlongitudinal axis of said shaft and a forth degree of freedom oftranslatory movement in the direction of said shaft.
 15. The simulatorapparatus of claim 14, wherein said holding device has for said thirdand forth degrees of freedom a gear arrangement that has a first bevelgear, which is connected to said shaft and co-rotates with the latterabout the longitudinal axis thereof and has a second and a third bevelgear which are arranged on either side of said first bevel gear and arein rolling engagement therewith.
 16. The simulator apparatus of claim15, wherein said first bevel gear is in rolling engagement with saidshaft via one or more pinions with the aid of a tooth system extendingalong said shaft.
 17. The simulator apparatus of claim 9, wherein saidholding device has for said third and forth degrees of freedom a geararrangement that has a first bevel gear, which is connected to saidshaft and co-rotates with the latter about the longitudinal axis thereofand has a second and a third bevel gear which are arranged on eitherside of said first bevel gear and are in rolling engagement therewith,and wherein said second and said third bevel gears are arrangedconcentrically with said shaft.
 18. The simulator apparatus of claim 9,wherein said holding device further is designed such that saidinstrument has a third degree of freedom of rotating movement about saidlongitudinal axis of said shaft and a forth degree of freedom oftranslatory movement in the direction of said shaft, and wherein saidgear arrangement is arranged in said spherical element.
 19. Thesimulator apparatus of claim 9, wherein said holding device further isdesigned such that said instrument has a third degree of freedom ofrotating movement about said longitudinal axis of said shaft and a forthdegree of freedom of translatory movement in the direction of saidshaft, and wherein said third and said forth degree of freedom areprovided with force feedback.
 20. The simulator apparatus of claim 19,wherein said second and third bevel gears are connected in each case toat least one actuator for said force feedback.
 21. The simulatorapparatus of claim 9, wherein in each case one-position detection sensoris provided for determining the position of said instrument for at leastone degree of freedom.
 22. The simulator apparatus of claim 9, whereinsaid instrument has a movable operating device and said movableoperating device is equipped with force feedback.
 23. The simulatorapparatus of claim 9, wherein said simulator apparatus is used forsimulating a minimally invasive intervention in the human or animalbody.